Additionally, each facet definition element can be uniquely
addressed via a URI constructed as follows:
Additionally, each facet usage in a built-in datatype definition
can be uniquely addressed via a URI constructed as follows:
For example, to address the usage of the maxInclusive facet in
the definition of int, the URI is:
3.1 Namespace considerations
The built-in datatypes defined by this specification
are designed to be used with the XML Schema definition language as well as other
XML specifications.
To facilitate usage within the XML Schema definition language, the built-in
datatypes in this specification have the namespace name:
- http://www.w3.org/2001/XMLSchema
To facilitate usage in specifications other than the XML Schema definition language,
such as those that do not want to know anything about aspects of the
XML Schema definition language other than the datatypes, each built-in
datatype is also defined in the namespace whose URI is:
- http://www.w3.org/2001/XMLSchema-datatypes
This applies to both
built-in primitive and
built-in derived datatypes.
Each user-derived datatype is also associated with a
unique namespace. However, user-derived datatypes
do not come from the namespace defined by this specification; rather,
they come from the namespace of the schema in which they are defined
(see XML Representation of
Schemas in [XML Schema Part 1: Structures]).
3.2 Primitive datatypes
The primitive datatypes defined by this specification
are described below. For each datatype, the
value space and lexical space
are defined, constraining facets which apply
to the datatype are listed and any datatypes derived
from this datatype are specified.
primitive datatypes can only be added by revisions
to this specification.
3.2.2 boolean
[Definition:] boolean has the
value space required to support the mathematical
concept of binary-valued logic: {true, false}.
3.2.2.1 Lexical representation
An instance of a datatype that is defined as boolean
can have the following legal literals {true, false, 1, 0}.
3.2.2.2 Canonical representation
The canonical representation for boolean is the set of
literals {true, false}.
3.2.3 decimal
[Definition:] decimal
represents arbitrary precision decimal numbers.
The value space of decimal
is the set of the values i × 10^-n,
where i and n are integers
such that n >= 0.
The order-relation on decimal
is: x < y iff y - x is positive.
[Definition:]
The value space of types derived from decimal
with a value for totalDigits of p
is the set of values i × 10^-n, where
n and i are integers such that
p >= n >= 0 and the number of significant decimal digits
in i is less than or equal to p.
[Definition:]
The value space of types derived from decimal
with a value for fractionDigits of s
is the set of values i × 10^-n, where
i and n are integers such
that 0 <= n <= s.
NOTE:
All minimally conforming processors must
support decimal numbers with a minimum of 18 decimal digits (i.e., with a
totalDigits of 18). However,
minimally conforming processors may
set an application-defined limit on the maximum number of decimal digits
they are prepared to support, in which case that application-defined
maximum number must be clearly documented.
3.2.3.1 Lexical representation
decimal has a lexical representation
consisting of a finite-length sequence of decimal digits (#x30-#x39) separated
by a period as a decimal indicator. If totalDigits is
specified, the number of digits must be less than or equal to
totalDigits.
If fractionDigits is specified, the
number of digits following the decimal point must be less than or equal to
the fractionDigits. An optional leading sign is allowed.
If the sign is omitted, "+" is assumed. Leading and trailing zeroes are optional.
If the fractional part is zero, the period and following zero(es) can
be omitted.
For example: -1.23, 12678967.543233, +100000.00, 210.
3.2.3.2 Canonical representation
The canonical representation for decimal is defined by
prohibiting certain options from the
Lexical representation (§3.2.3.1). Specifically, the preceding
optional "+" sign is prohibited. The decimal point is required. Leading and
trailing zeroes are prohibited subject to the following: there must be at least
one digit to the right and to the left of the decimal point which may be a zero.
3.2.3.4 Derived datatypes
The following built-in
datatypes are derived from
decimal:
3.2.4 float
[Definition:] float corresponds
to the IEEE single-precision 32-bit floating point type
[IEEE 754-1985]. The basic value space of
float consists of the values
m × 2^e, where m
is an integer whose absolute value is less than
2^24, and e is an integer
between -149 and 104, inclusive. In addition to the basic
value space described above, the
value space of float also contains the
following special values: positive and negative zero,
positive and negative infinity and not-a-number.
The order-relation on float
is: x < y iff y - x is positive.
Positive zero is greater than negative zero. Not-a-number equals itself and is
greater than all float values including positive infinity.
A literal in the lexical space representing a
decimal number d maps to the normalized value
in the value space of float that is
closest to d; if d is
exactly halfway between two such values then the even value is chosen.
This is the best approximation of d
[Clinger, WD (1990)][Gay, DM (1990)], which is more
accurate than the mapping required by [IEEE 754-1985].
3.2.4.1 Lexical representation
float values have a lexical representation
consisting of a mantissa followed, optionally, by the character
"E" or "e", followed by an exponent. The exponent must
be an integer. The mantissa must be a decimal number. The representations
for exponent and mantissa must follow the lexical rules for
integer and decimal. If the "E" or "e" and
the following exponent are omitted, an exponent value of 0 is assumed.
The special values positive and negative zero, positive
and negative infinity and not-a-number have lexical representations 0,
-0, INF, -INF and
NaN, respectively.
For example, -1E4, 1267.43233E12, 12.78e-2, 12 and INF
are all legal literals for float.
3.2.4.2 Canonical representation
The canonical representation for float is defined by
prohibiting certain options from the
Lexical representation (§3.2.4.1). Specifically, the exponent
must be indicated by "E". Leading zeroes are prohibited in the exponent.
For the mantissa, the preceding optional "+" sign is prohibited
and the decimal point is required.
Leading and trailing zeroes are prohibited subject to the following:
number representations must
be normalized such that there is a single
digit to the left of the decimal point and at least a single digit to the
right of the decimal point.
3.2.5 double
[Definition:] The double
datatype corresponds to IEEE double-precision 64-bit floating point
type [IEEE 754-1985]. The basic value space
of double consists of the values
m × 2^e, where m
is an integer whose absolute value is less than
2^53, and e is an
integer between -1075 and 970, inclusive. In addition to the basic
value space described above, the
value space of double also contains
the following special values: positive and negative zero,
positive and negative infinity and not-a-number.
The order-relation on double
is: x < y iff y - x is positive.
Positive zero is greater than negative zero. Not-a-number equals itself and is
greater than all double values including positive infinity.
A literal in the lexical space representing a
decimal number d maps to the normalized value
in the value space of double that is
closest to d; if d is
exactly halfway between two such values then the even value is chosen.
This is the best approximation of d
([Clinger, WD (1990)], [Gay, DM (1990)]), which is more
accurate than the mapping required by [IEEE 754-1985].
3.2.5.1 Lexical representation
double values have a lexical representation
consisting of a mantissa followed, optionally, by the character "E" or
"e", followed by an exponent. The exponent must be
an integer. The mantissa must be a decimal number. The representations
for exponent and mantissa must follow the lexical rules for
integer and decimal. If the "E" or "e"
and the following exponent are omitted, an exponent value of 0 is assumed.
The special values positive and negative zero, positive
and negative infinity and not-a-number have lexical representations 0,
-0, INF, -INF and
NaN, respectively.
For example, -1E4, 1267.43233E12, 12.78e-2, 12 and INF
are all legal literals for double.
3.2.5.2 Canonical representation
The canonical representation for double is defined by
prohibiting certain options from the
Lexical representation (§3.2.5.1). Specifically, the exponent
must be indicated by "E". Leading zeroes are prohibited in the exponent.
For the mantissa, the preceding optional "+" sign is prohibited
and the decimal point is required.
Leading and trailing zeroes are prohibited subject to the following:
number representations must
be normalized such that there is a single
digit to the left of the decimal point and at least a single digit to the
right of the decimal point.
3.2.6 duration
[Definition:] duration represents a duration of time.
The value space of duration is
a six-dimensional space where the coordinates
designate the Gregorian year, month, day, hour, minute, and second components defined in
§ 5.5.3.2 of [ISO 8601],
respectively. These components are ordered
in their significance by their order of appearance i.e. as year, month, day,
hour, minute, and second.
3.2.6.1 Lexical representation
The lexical representation for duration is the
[ISO 8601] extended format PnYn
MnDTnH nMnS, where
nY represents the number of years, nM the
number of months, nD the number of days, 'T' is the
date/time separator, nH the number of hours,
nM the number of minutes and nS the
number of seconds. The number of seconds can include decimal digits
to arbitrary precision.
The values of the
Year, Month, Day, Hour and Minutes components are not restricted but
allow an arbitrary integer. Similarly, the value of the Seconds component
allows an arbitrary decimal. Thus, the lexical representation of
duration does not follow the alternative
format of § 5.5.3.2.1 of [ISO 8601].
An optional preceding minus sign ('-') is
allowed, to indicate a negative duration. If the sign is omitted a
positive duration is indicated. See also ISO 8601 Date and Time Formats (§D).
For example, to indicate a duration of 1 year, 2 months, 3 days, 10
hours, and 30 minutes, one would write: P1Y2M3DT10H30M.
One could also indicate a duration of minus 120 days as:
-P120D.
Reduced precision and truncated representations of this format are allowed
provided they conform to the following:
-
The lowest order items may be omitted. If omitted their value is
assumed to be zero.
-
The lowest order item may have a decimal fraction.
-
If the number of years, months, days, hours, minutes, or seconds in any
expression equals zero, the number and its corresponding designator may
be omitted. However, at least one number and its designator must be present.
-
The designator 'T' shall be absent if all of the time items are absent.
The designator 'P' must always be present.
For example, P1347Y, P1347M and P1Y2MT2H are all allowed;
P0Y1347M and P0Y1347M0D are allowed. P-1347M is not allowed although
-P1347M is allowed. P1Y2MT is not allowed.
3.2.6.2 Order relation on duration
In general, the order-relation on duration
is a partial order since there is no determinate relationship between certain
durations such as one month (P1M) and 30 days (P30D).
The order-relation
of two duration values x and
y is x <= y iff s+x <= s+y
for each qualified dateTime (§3.2.7) s
in the list below. These values for s cause the greatest deviations in the addition of
dateTimes and durations. Addition of durations to time instants is defined
in Adding durations to dateTimes (§E).
- 1696-09-01T00:00:00Z
- 1697-02-01T00:00:00Z
- 1903-03-01T00:00:00Z
- 1903-07-01T00:00:00Z
The following table shows the strongest relationship that can be determined
between example durations. The symbol <> means that the order relation is
indeterminate. Note that because of leap-seconds, a seconds field can vary
from 59 to 60. However, because of the way that addition is defined in
Adding durations to dateTimes (§E), they are still totally ordered.
| | Relation |
| P1Y | > P364D | >= P365D | | <= P366D | < P367D |
| P1M | > P27D | >= P28D | <> P29D | <> P30D | <= P31D | < P32D |
| P5M | > P149D | >= P150D | <> P151D | <> P152D | <= P153D | < P154D |
Implementations are free to optimize the computation of the ordering relationship. For example, the following table can be used to
compare durations of a small number of months against days.
| | Months | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | ... |
| Days | Minimum | 28 | 59 | 89 | 120 | 150 | 181 | 212 | 242 | 273 | 303 | 334 | 365 | 393 | ... |
| Maximum | 31 | 62 | 92 | 123 | 153 | 184 | 215 | 245 | 276 | 306 | 337 | 366 | 397 | ... |
3.2.6.4 Totally ordered durations
Certain derived datatypes of durations can be guaranteed have a total order. For
this, they must have fields from only one row in the list below and the time zone
must either be required or prohibited.
- year, month
- day, hour, minute, second
For example, a datatype could be defined to correspond to the
[SQL] datatype Year-Month interval that required a four digit
year field and a two digit month field but required all other fields to be unspecified. This datatype could be defined as below and would have a total order.
<simpleType name='SQL-Year-Month-Interval'>
<restriction base='duration'>
<pattern value='P\p{Nd}{4}Y\p{Nd}{2}M'/>
</restriction>
</simpleType>
|
3.2.7 dateTime
[Definition:] dateTime represents a specific instant of time. The
value space of dateTime is the space
of Combinations of date and time of day values as defined
in § 5.4 of [ISO 8601].
3.2.7.1 Lexical representation
A single lexical representation, which is a subset of the lexical
representations allowed by [ISO 8601], is allowed for
dateTime. This lexical representation is the
[ISO 8601] extended format CCYY-MM-DDThh:mm:ss
where "CC" represents the century, "YY" the year, "MM" the month and
"DD" the day, preceded by an optional leading "-" sign to indicate a
negative number. If the sign is omitted, "+" is assumed. The letter
"T" is the date/time separator and "hh", "mm", "ss" represent hour,
minute and second respectively. Additional digits can be used to
increase the precision of fractional seconds if desired i.e the format
ss.ss... with any number of digits after the decimal point is supported.
To accommodate
year values greater than 9999 additional digits can be added to the
left of this representation. The year 0000 is prohibited.
This representation may be immediately followed by a "Z" to indicate
Coordinated Universal Time (UTC) or, to indicate the time zone, i.e. the
difference between the local time and Coordinated Universal Time,
immediately followed by a sign,
+ or -, followed by the difference from UTC represented as hh:mm.
See ISO 8601 Date and Time Formats (§D) for details about legal values in the
various fields.
For example, to indicate 1:20 pm on May the 31st, 1999 for Eastern
Standard Time which is 5 hours behind Coordinated Universal Time (UTC), one
would write: 1999-05-31T13:20:00-05:00.
3.2.7.2 Canonical representation
The canonical representation for dateTime is defined
by prohibiting certain options from the
Lexical representation (§3.2.7.1).
Specifically, either the time zone must
be omitted or, if present, the time zone must be Coordinated Universal
Time (UTC) indicated by a "Z".
3.2.7.3 Order relation on dateTime
In general, the order-relation on dateTime
is a partial order since there is no determinate relationship between certain
instants. For example, there is no determinate
ordering between
(a)
2000-01-20T12:00:00 and (b) 2000-01-20T12:00:00Z. Based on
timezones currently in use, (c) could vary from 2000-01-20T12:00:00+12 to
2000-01-20T12:00:00-13. It is, however, possible for this range to expand or
contract in the future, based on local laws. Because of this, the following
definition uses a somewhat broader range of indeterminate values: +14..-14.
The following definition uses the notation S[year] to represent the year
field of S, S[month] to represent the month field, and so on. The notation (Q
& "-14") means adding the timezone -14 to Q, where Q did not
already have a timezone. This is a logical explanation of the process. Actual
implementations are free to optimize as long as they produce the same results.
The ordering between two dateTimes P and Q is defined by the following
algorithm:
A.Normalize P and Q. That is, if there is a timezone present, but
it is not Z, convert it to Z using the addition operation defined in
Adding durations to dateTimes (§E)
- Thus 2000-03-04T23:00:00+03 normalizes to 2000-03-05T02:00:00Z
B. If P and Q either both have a time zone or both do not have a time
zone, compare P and Q field by field from the year field down to the
second field, and return a result as soon as it can be determined. That is:
-
For each i in {year, month, day, hour, minute, second}
- If P[i] and Q[i] are both not specified, continue to the next i
- If P[i] is not specified and Q[i] is, or vice versa, stop and return
P <> Q
- If P[i] < Q[i], stop and return P < Q
- If P[i] > Q[i], stop and return P > Q
- Stop and return P = Q
C.Otherwise, if P contains a time zone and Q does not, compare
as follows:
- P <= Q if P <= (Q with time zone -14)
- P >= Q if P >= (Q with time zone +14)
- P <> Q otherwise, that is, if (Q with time zone -14) < P < (Q with time zone +14)
D. Otherwise, if P does not contain a time zone and Q does, compare
as follows:
- P <= Q if (P with time zone +14) <= Q.
- P >= Q if (P with time zone -14) >= Q.
- P <> Q otherwise, that is, if (P with time zone -14) < Q < (P with time zone +14)
Examples:
| Determinate | Indeterminate |
| 2000-01-15T00:00:00 < 2000-02-15T00:00:00 | 2000-01-01T12:00:00 <>
1999-12-31T23:00:00Z |
| 2000-01-15T12:00:00 < 2000-01-16T12:00:00Z | 2000-01-16T12:00:00 <>
2000-01-16T12:00:00Z |
| | 2000-01-15T00:00:00 <> 2000-01-16T12:00:00Z |
3.2.7.4 Totally ordered dateTimes
Certain derived types from dateTime
can be guaranteed have a total order. To
do so, they must require that a specific set of fields are always specified, and
that remaining fields (if any) are always unspecified. For example, the date
datatype without time zone is defined to contain exactly year, month, and day.
Thus dates without time zone have a total order among themselves.
3.2.8 time
[Definition:] time
represents an instant of time that recurs every day. The
value space of time is the space
of time of day values as defined in § 5.3 of
[ISO 8601]. Specifically, it is a set of zero-duration daily
time instances.
Since the lexical representation allows an optional time zone
indicator, time values are partially ordered because it may
not be able to determine the order of two values one of which has a
time zone and the other does not. The order relation on
time values is the
Order relation on dateTime (§3.2.7.3) using an arbitrary date. See also
Adding durations to dateTimes (§E). Pairs of time values with or without time zone indicators are totally ordered.
3.2.8.1 Lexical representation
The lexical representation for time is the left
truncated lexical representation for dateTime:
hh:mm:ss.sss with optional following time zone indicator. For example,
to indicate 1:20 pm for Eastern Standard Time which is 5 hours behind
Coordinated Universal Time (UTC), one would write: 13:20:00-05:00. See also
ISO 8601 Date and Time Formats (§D).
3.2.8.2 Canonical representation
The canonical representation for time is defined
by prohibiting certain options from the
Lexical representation (§3.2.8.1). Specifically, either the time zone must
be omitted or, if present, the time zone must be Coordinated Universal
Time (UTC) indicated by a "Z".
3.2.9 date
[Definition:] date
represents a calendar date. The value space
of date is the set of Gregorian calendar dates as defined
in § 5.2.1 of [ISO 8601]. Specifically,
it is a set of one-day long, non-periodic instances
e.g. lexical 1999-10-26 to represent the calendar date 1999-10-26, independent
of how many hours this day has.
Since the lexical representation allows an optional time zone
indicator, date values are partially ordered because it may
not be possible to unequivocally determine the order of two values one of which has a
time zone and the other does not. If
date values are considered as periods of time, the order relation
on date values is the order relation on their starting instants.
This is discussed in Order relation on dateTime (§3.2.7.3). See also
Adding durations to dateTimes (§E). Pairs of date values with or without time zone indicators are totally ordered.
3.2.9.1 Lexical representation
The lexical representation for date is the reduced (right
truncated) lexical representation for dateTime:
CCYY-MM-DD. No left truncation is allowed. An optional following time
zone qualifier is allowed as for dateTime. To
accommodate year values outside the range from 0001 to 9999, additional
digits can be added to the left of this representation and a preceding "-"
sign is allowed.
For example, to indicate May the 31st, 1999, one would write: 1999-05-31.
See also ISO 8601 Date and Time Formats (§D).
3.2.10 gYearMonth
[Definition:] gYearMonth represents a
specific gregorian month in a specific gregorian year. The
value space of gYearMonth
is the set of Gregorian calendar months as defined in § 5.2.1 of
[ISO 8601]. Specifically, it is a set of one-month long,
non-periodic instances
e.g. 1999-10 to represent the whole month of 1999-10, independent of
how many days this month has.
Since the lexical representation allows an optional time zone
indicator, gYearMonth values are partially ordered because it may
not be possible to unequivocally determine the order of two values one of
which has a time zone and the other does not. If gYearMonth
values are considered as periods of time, the order relation on
gYearMonth values is the order relation on their starting instants.
This is discussed in Order relation on dateTime (§3.2.7.3). See also
Adding durations to dateTimes (§E). Pairs of gYearMonth
values with or without time zone indicators are totally ordered.
NOTE:
Because month/year combinations in one calendar only rarely correspond
to month/year combinations in other calendars, values of this type
are not, in general, convertible to simple values corresponding to month/year
combinations in other calendars. This type should therefore be used with caution
in contexts where conversion to other calendars is desired.
3.2.10.1 Lexical representation
The lexical representation for gYearMonth is the reduced
(right truncated) lexical representation for dateTime:
CCYY-MM. No left truncation is allowed. An optional following time
zone qualifier is allowed. To accommodate year values outside the range from 0001 to 9999, additional digits
can be added to the left of this representation and a preceding "-" sign is allowed.
For example, to indicate the month of May 1999, one would write: 1999-05.
See also ISO 8601 Date and Time Formats (§D).
3.2.11 gYear
[Definition:] gYear represents a
gregorian calendar year. The value space of
gYear is the set of Gregorian calendar years as defined in
§ 5.2.1 of [ISO 8601]. Specifically, it is a set of one-year
long, non-periodic instances
e.g. lexical 1999 to represent the whole year 1999, independent of
how many months and days this year has.
Since the lexical representation allows an optional time zone
indicator, gYear values are partially ordered because it may
not be possible to unequivocally determine the order of two values one of which has a
time zone and the other does not. If
gYear values are considered as periods of time, the order relation
on gYear values is the order relation on their starting instants.
This is discussed in Order relation on dateTime (§3.2.7.3). See also
Adding durations to dateTimes (§E). Pairs of gYear values with or without time zone indicators are totally ordered.
NOTE:
Because years in one calendar only rarely correspond to years
in other calendars, values of this type
are not, in general, convertible to simple values corresponding to years
in other calendars. This type should therefore be used with caution
in contexts where conversion to other calendars is desired.
3.2.11.1 Lexical representation
The lexical representation for gYear is the reduced (right
truncated) lexical representation for dateTime: CCYY.
No left truncation is allowed. An optional following time
zone qualifier is allowed as for dateTime. To
accommodate year values outside the range from 0001 to 9999, additional
digits can be added to the left of this representation and a preceding
"-" sign is allowed.
For example, to indicate 1999, one would write: 1999.
See also ISO 8601 Date and Time Formats (§D).
3.2.12 gMonthDay
[Definition:] gMonthDay is a gregorian date that recurs, specifically a day of
the year such as the third of May. Arbitrary recurring dates are not
supported by this datatype. The value space of
gMonthDay is the set of calendar
dates, as defined in § 3 of [ISO 8601]. Specifically,
it is a set of one-day long, annually periodic instances.
Since the lexical representation allows an optional time zone
indicator, gMonthDay values are partially ordered because it may
not be possible to unequivocally determine the order of two values one of which has a
time zone and the other does not. If
gMonthDay values are considered as periods of time, the order relation
on gMonthDay values is the order relation on their starting instants.
This is discussed in Order relation on dateTime (§3.2.7.3). See also
Adding durations to dateTimes (§E). Pairs of gMonthDay values with or without time zone indicators are totally ordered.
NOTE:
Because day/month combinations in one calendar only rarely correspond
to day/month combinations in other calendars, values of this type do not,
in general, have any straightforward or intuitive representation
in terms of most other calendars. This type should therefore be
used with caution in contexts where conversion to other calendars
is desired.
3.2.12.1 Lexical representation
The lexical representation for gMonthDay is the left
truncated lexical representation for date: --MM-DD.
An optional following time
zone qualifier is allowed as for date.
No preceding sign is allowed. No other formats are allowed. See also
